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Re: Selectivity of "=" (Re: [HACKERS] Index not used on simple se lect)

From: Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>
To: Zeugswetter Andreas IZ5 <Andreas(dot)Zeugswetter(at)telecom(dot)at>
Cc: pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: Selectivity of "=" (Re: [HACKERS] Index not used on simple se lect)
Date: 1999-07-28 16:07:21
Message-ID: 199907281607.MAA11812@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
> Example assuming int index column:
> from	to	nrow_estimate
> 1	100	10005
> 101	20000	9997
> 20001	100000	10014
> 
> badly scewed values (excluded in above table):
> val		nrow_estimate
> 1		100000
> 5		1000000
> 
> But imho this is an overkill, and seldom useful.

Yes, some commerical databases do this, though it is of questionable value.

-- 
  Bruce Momjian                        |  http://www.op.net/~candle
  maillist(at)candle(dot)pha(dot)pa(dot)us            |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

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